Town Population

Date: 05/03/97 at 05:04:26
From: Elicia
Subject: Story Sums
The population of town A is 4800 more than town B. If 3100 people move
from town B to town A, the population in town A will be 11 times that
of town B. Find the original, total population of the two towns.
I did this:
10 units = 4800+3100+7900
1 unit = 7900/10 =790
790+3100 = 3890
Town B----3890
3890+4800 = 8690
Town A----8690
8690+3890 = 12580
The total population of the two towns at first is 12580, but my
teacher said this is wrong.

Date: 05/03/97 at 07:12:49
From: Doctor Anthony
Subject: Re: Story Sums
With this type of problem it is better to use symbols like x or y to
represent unknown numbers. You can then write down equations, using
these letters, to show what happens as you follow the instructions
given in the question.
Let x = initial population of town B
x+4800 = initial population of town A
Now move 3100 people from B to A:
New population of B = x-3100
New population of A = x+4800+3100
Now the second of these is 11 times the first, so:
x+4800+3100 = 11(x-3100)
x+7900 = 11x-34100
7900+34100 = 10x
42000 = 10x
x = 4200
Initial population of B was 4200
Initial population of A was 9000
The total for both towns = 4200 + 9000 = 13200
-Doctor Anthony, The Math Forum
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